A Unidirectional Current-Fed DC-DC Converter with Low Cost and High Efficiency for EV Systems

APM in EV systems imposes high requirements on dc-dc converters, for instance, high current handling capability, wide voltage range adaptability and high reliability. It is difficult for existing converters to fulfill these requirements while controlling cost. This article proposes a unidirectional current-fed dc-dc converter composed of diodes and MOSFETs for maintaining high efficiency while saving active switches. The proposal is constructed on the basis of current-fed dual-activebridge (CFDAB). It shares some of the switches of CFDAB to add another LLC-based power channel. This allows currents to be freely allocated between two channels. By adjusting channel currents, the currents on part of the switches can be kept reversed over the entire switching cycle, allowing the use of diodes, and saving cost. Meanwhile, the original merits of CFDAB, e.g., high output current quality, high efficiency over wide voltage range, and excellent soft-switching performance, are retained in the proposal. Hence, the proposal is a good candidate for APM.